Download or read book HIGH CURRENT LONG PULSE GYROTRON BACKWARD WAVE OSCILLATOR EXPERIMENTS written by THOMAS ALLEN SPENCER and published by . This book was released on 1991 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: the existence of the gyro-backward-wave, as well as show the magnetic tunability of the gyrotron-backward-wave. In the solid beam case (1-2 kA), about 300-800 kW of extracted microwave power was detected in the waveguide detection system, implying that approximately 3-8 MW (efficiency $\sim$1-2%) of power is generated from the gyro-BWO device. The pulselengths for the solid beam case were from 300-600 ns (essentially the total flat-top voltage pulselength) over a frequency range of 4.5-6 GHz. The

Download or read book Effects of Tapering on High Current Long Pulse Gyrotron Backward Wave Oscillator Experiments written by Mark Thomas Walter and published by . This book was released on 1995 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Power Ultra Long Pulsed Gyrotron Backward Wave Oscillators written by and published by . This book was released on 1995 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research program was to explore tapering of interaction tubes and magnetic fields as techniques for enhancing the performance of high power microwave gyrotron-backward-wave- oscillators (gyro-BWOs). Experiments were performed on the Michigan Electron Long-Beam Accelerator, (MELBA), which operated with parameters: voltage=O.7-O.9 MV, diode current = 1-10 kA, injected current = 1-4 kA, and pulselengths of 0.5-i microsecond. Microwave emission frequency was in the range from 4.5-6 GHz. Experiments on the fundamental cyclotron wave showed peak microwave tube power up to 40-55 MW over shortened pulselengths (

Download or read book FY92 Progress Report for the Gyrotron Backward Wave Oscillator Experiment written by and published by . This book was released on 1993 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental and theoretical analyses, including particle-in-cell computer code simulations, are presented for the Gyrotron Backward Wave oscillator (Gyro-BWO) highpower microwave device. The Gyro-BWO has been designed, constructed, and initially tested as a frequency tunable device. The design has concentrated on a TE01, 4- to 6- GHz annular beam device. The annular beam is produced by the RAMBO pulser, which has a diode voltage of -300 to -800 kV and diode current of 1 to 20 kA. Initial results have shown that the device is operating in the backward wave mode. Initial results have also demonstrated that the device is magnetically tunable; that is, the frequency is tunable by adjusting the magnetic field. A Vlasov-type antenna is used for the extraction of the microwave signal on the diode end of the experiment, with initial power extraction of up to 2 MW ... High power microwave, HPM, Gyro-BWO, Gyrotron, Gyrotron backward wave oscillator.

Download or read book State of the Art of High Power Gyro Devices and Free Electron Masers Update 2015 KIT Scientific Reports 7717 written by Thumm, Manfred and published by KIT Scientific Publishing. This book was released on 2016-08-29 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A W band Gyrotron Backward Wave Oscillator with Helically Corrugated Waveguide written by Craig Ross Donaldson and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of a successful W-band gyrotron backward wave oscillator experiment. Three major achievements presented in this thesis are: 1) The design, simulation, construction and operation of a cusp electron gun; 2) The design, simulation, optimisation, construction and experimental measurement of a W-band helically corrugated waveguide and 3) the operation of the world's first W-band gyro-BWO using both a helically corrugated waveguide and a cusp electron gun. Gyro-BWO interaction with a 2nd cyclotron harmonic axis-encircling annular electron beam was observed. The interaction region was constructed through an accurate electroplating method while the designed dispersion characteristics agreed well to the experimental measurements. The loss through the optimised construction method was low, recorded around 1dB through the frequency range of interest. The following work presents the analytical, numerical and experimental investigation of a proof of principle gyro-BWO experiment. The design, simulation and optimisation of a thermionic cusp electron gun that can generate a 1.5A, 40kV axisencircling electron beam are discussed. Simulations showed a high quality electron beam with ~8% velocity spread and ~10% alpha spread. Experiments were conducted using this electron gun and the accelerating voltage pulse, diode current, transported beam current are presented. The electron beam profile was recorded showing a clear axis-encircling beam image from which the electron beam diameter and alpha values can be measured. Microwave radiation was measured over a frequency range of ~91-100GHz with a approximate maximum power of ~0.37kW. Operating over the magnetic field range 1.79T to 1.9T and measured over a range of alpha values this result was very impressive and proved the successful operation of the gyro-BWO.

Download or read book State of the Art of High Power Gyro Devices and Free Electron Masers Update 2017 KIT Scientific Reports 7750 written by Thumm, Manfred and published by KIT Scientific Publishing. This book was released on 2018-06-04 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book State of the Art of High Power Gyro Devices Update of Experimental Results 2021 KIT Scientific Reports 7761 written by Thumm, Manfred and published by KIT Scientific Publishing. This book was released on 2021-10-28 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents an update of the experimental achievements published in the review “State- of-the-Art of High-Power Gyro-Devices and Free Electron Masers”, Journal of Infrared, Millime-ter, and Terahertz Waves, 41, No. 1, pp 1-140 (2020) related to the development of gyro-devices (Tables 2-34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for any applications.

Download or read book State of the Art of High Power Gyro Devices and Free Electron Masers Update 2016 KIT Scientific Reports 7735 written by Thumm, Manfred and published by KIT Scientific Publishing. This book was released on 2017-07-19 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book State of the Art of High Power Gyro Devices Update of Experimental Results 2023 KIT Scientific Reports 7765 written by Thumm, Manfred and published by KIT Scientific Publishing. This book was released on 2024-02-06 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents an update of the experimental achievements published in the review “State- of-the-Art of High-Power Gyro-Devices and Free Electron Masers”, Journal of Infrared, Millimeter, and Terahertz Waves, 41, No. 1, pp 1-140 (2020) and in the KIT Scientific Report 7761 (2021), related to the development of gyro-devices (Tables 2-34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for any applications.

Download or read book Theoretic and Experimental Investigation of Gyrotron Backward wave Oscillator with High Efficiency and Broad band Capabilities written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Study of an Injection Locked Gyrotron Backward Wave Oscillator written by C. S. Kou and published by . This book was released on 1990* with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Energy Recovery System for a Gyrotron Backward Wave Oscillator written by Liang Zhang and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is based on the research project of a W-band gyrotron backward wave oscillator (gyro-BWO) using a helically corrugated waveguide which is currently being built and upgraded in the University of Strathclyde. The gyro-BWO was optimally designed through numerical simulations to achieve an output maximum power of ~ 10 kW with a -3 dB frequency tuning range of 84 - 104 GHz. To increase the overall efficiency of the W-band gyro-BWO, an energy recovery system of four-stage depressed collector was designed, numerically optimized and fabricated on the gyro-BWO. Microwave components including the Bragg reflectors, the side-wall coupler, the three-layer microwave window and the pillbox window were designed, simulated and measured to facilitate the practical use of the energy recovery system. This thesis includes the analytically calculated results, the numerical simulations as well as the experimental results of the said components and system. A 14-section Bragg reflector together with the side-wall coupler located at the upstream of the helically corrugated interaction cavity was used to couple the microwave radiation out. This allowed the installation of the depressed collector at the downstream side of the gyro-BWO. The transmission coefficient of the coupler was numerically optimized to achieve -1.0 dB over the frequency tuning range, from 84 - 104 GHz. The Bragg reflector measurement agrees well with the simulation. The input coupler achieves an average -13 dB reflection over the frequency in the measurement. Theoretical analysis of the pillbox type window and multi-layer window based on mode-matching method was carried out. The simulation and optimization of the pillbox window achieved a reflection of less than -15 dB in the whole operating frequency range of 84 - 104 GHz. The three-layer window can achieve less than 30 dB reflection in the frequency range of 84 - 104 GHz in the simulation. A three-layer window and a pillbox window which particularly optimized in frequency range of 90 - 100 GHz (the operating frequency range of the gyro- TW A that shares the same experimental setup as the gyro-BWO) were fabricated. With manufacturing constraints the design of the three-layer window achieved an average -10 dB measured reflection in 84 - 104 GHz and better than -15 dB in 90 - 100 GHz. In the downstream side of the gyro-BWO, another 18-section Bragg reflector was used to reflect the radiation back into the upstream interaction cavity. And the transmission coefficient of -30 dB was obtained in the microwave measurements using a VNA, which means the microwave power leakage was less than 1%. The measurement results agreed well with the simulations. A four-stage depressed collector was designed to recover the energy from the spent electrons. The 3D PlC code MAGIC and a genetic algorithm were used to simulate and optimize the geometry of the electrodes. Secondary electron emissions were simulated and a few emission models were compared to investigate their effects on the overall recovery efficiency and the backstreaming rate for the multistage collector. The optimization of the shape and dimensions of each stage of the collector using a genetic algorithm achieved an overall recovery efficiency of about 70%, with a minimized backstreaming rate of 4.9%. The heat distribution on the collector was calculated and the maximum heat density on the electrodes was 240W/cm2 and the generation of "hot spots" could be avoided. The electric field distribution inside the depressed collector was calculated and the geometries of these electrodes were properly shaped to avoid the voltage breakdown in vacuum.

Download or read book Repetitively Pulsed Backward Wave Oscillator Investigations written by and published by . This book was released on 1994 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Pulsed Power and Plasma Science Laboratory at the University of New Mexico (UNM) has completed its initial phase of research on repetitively pulsed high power backward-wave oscillators (BWOs). The aggressive program that we had established seeked to address three basic goals: (1) Understand the physics of high efficiency vacuum BWOs using the Sinus-6 repetitively pulsed electron beam accelerator, (2) study vacuum and initiate plasma-filled long pulse BWO operations using the modified PI-110A accelerator, and (3) Study the prospects of incorporating ferroelectric ceramic cathodes in high power electron beam-driven microwave sources to improve their operations in the long pulse regime.

Download or read book Experimental and Theoretical Studies of High Power Plasma Filled Backward Wave Oscillators written by and published by . This book was released on 1991 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of the research covered during this period was to study the behavior of a plasma loaded BWO when driven by large beam current approaching the vacuum space charge limiting value inside the device. The main results are: (1) The plasma indeed allows injection of large current into the BWO. Currents as high as 75% of the vacuum space charge limit were successfully propagated. (2) In plasma loaded BWO, in contrast to the vacuum case, the enhanced efficiency can be maintained even for large beam currents (approaching the vacuum limit). It is anticipated that this might hold even well beyond the vacuum limit. (3) The output frequency is only slightly shifted (1%-5%) by the presence of the plasma. (4) A foilless field emission diode can operate successfully in a background of low density plasma. (5) An important parameter, the start oscillation current was measured for the first time in vacuum BWO for various beam voltages and geometries. For example, at 600 kV the start current is under 140 A. (6) Initial indications are that the plasma increases the microwave pulse duration. (7) A novel field emission cathode design (new geometries and materials) allows for continuous control of the beam current in the range of 50-6000 Amps. Turn on fields below 50kV/cm were achieved. (8) Linear theory for a plasma loaded BWO was developed (using a simplified model). and (9) A nonlinear theory for a finite length device was developed.

Download or read book Experimental Study of a High Efficiency Step tunable MW Gyrotron Oscillator written by David Samuel Tax and published by . This book was released on 2013 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: The gyrotron is a source capable of producing megawatt power levels at millimeter-wave frequencies for many important applications, including electron cyclotron heating and current drive in magnetic fusion devices. It is important that the gyrotron operates with high efficiency and provides a high quality output beam to minimize system size, maximize reliability and avoid additional losses in external systems. This thesis presents the experimental study of such a gyrotron designed to operate at MW power levels and whose initial 110 GHz operation was expanded to include operation at 124.5 GHz. To this end, a new set of components, including a cavity, mode converter, and output window were designed for operation at both frequencies. The cavity was designed using the code MAGY and the Q factors of 830 for the TE22,6,1mode at 110 GHz and 1060 for the TE24,7,1 mode at 124.5 GHz would be suitable for CW operation in an industrial gyrotron. The mode converter consisting of a dimpled-wall launcher and 4 phasecorrecting mirrors could theoretically produce an output beam with 99 % Gaussian beam content at each frequency while a single-disc window was implemented with over 99.5 % power transmission at both frequencies. The achieved output power in experiment was 1.1 MW at 110 GHz and 850 kW at 124.5 GHz for the design parameters of 96 kV and 40 A. At 98 kV and 42 A, the gyrotron achieved 1.25 MW and 1 MW at 110 and 124.5 GHz, respectively. Mode competition is typically a major limitation in such gyrotrons, and stable single-mode operation was demonstrated at both frequencies. At 110 GHz, the output beam had 98.8 % Gaussian beam content, while at 124.5 GHz, the output beam quality was 94.4 %. Another experiment within this thesis demonstrated the implementation of a mode converter with smooth mirrors that would be less susceptible to machining and misalignment errors. A Gaussian beam content of 96 % was measured in that experiment. In addition, a thorough study of the gyrotron start-up scenario was performed, for which experimental work had been lacking in the literature. The start-up scenario is the sequence of modes that are excited during the rise of the voltage pulse and is essential for the gyrotron to operate in its most efficient regime known as the hard self-excitation regime. This gyrotron operates nominally in the TE22,6,1 mode near the 110 GHz cutoff frequency with an axial field profile that is approximately Gaussian at the steady-state peak voltage. In experiments performed in the smooth mirror mode converter configuration, lower frequency modes were observed at lower voltages as opposed to higher frequency modes as predicted by theory. Analysis of these modes showed that they are backward-wave modes far from their cutoff frequency which have higher order axial field profiles, i.e. TE21,6,3 and TE21,6,4 modes at frequencies of 108-109 GHz. The excitation of these modes was investigated and shown to be possible by using theory and single-mode simulations with the code MAGY. This discovery was important as these modes were not included in past code runs, and thus future improvements can be made to incorporate this effect.

Download or read book Experimental Excitation and Reduction of the Beam Breakup Instability in Long pulse Electron Beam Transport written by Peter Richard Menge and published by . This book was released on 1993 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: